1. Field of the Invention
This invention relates to a rubber extruder, more particularly to a rubber extruder with a screw rod for extruding a rubber or rubber-like material from the rubber extruder.
2. Description of the Related Art
Conventional rubber extruders (see FIG. 1), such as those disclosed in U.S. Pat. Nos. 5,679,293, 5,486,104, 4,850,839, and 4,565,512, normally include a cylindrical barrel 11 adapted to receive a rubber or rubber-like material therein, and a hydraulic operated ram 121 disposed movably in a hydraulic cylinder 12 and extending into the cylindrical barrel 11 for extruding the rubber material through an extrusion die (not shown). A cutter 13 is disposed downstream of the extrusion die for periodically cutting the resultant extruded material into pieces of extrudate of equal dimensions.
Since the hydraulic operated ram 121 is made from metal, it will be subjected to expansion or contraction as a result of variation of the temperature of hydraulic oil entering into the hydraulic cylinder 12, thereby affecting the advancing speed of the hydraulic operated ram 121. As a consequence, the advancing speed of the extrudate is correspondingly affected, thereby resulting in non-uniform dimensions of the pieces of the extrudate. In addition, the resistance to advancing movement of the hydraulic operated ram 121 is higher when a higher amount of the rubber material is present in the barrel 11. As such, the advancing speed of the hydraulic operated ram 121 will vary along with the variation of the amount of the rubber material present in the barrel 11. Moreover, the hydraulic oil for driving the hydraulic operated ram 121 is required to be periodically replaced with fresh hydraulic oil, and has to be disposed according to the requirements of local environmental regulations.